That's true. I've used some pretty good finders, but they are still dependent on the lens speed. I'm happy with my 35 f2.8 Distagon, but not with focusing it indoors. With a Leica, or similar, that isn't a factor.
I agree that SLRs can provide a struggle with focus in low light, the advantage for the rangefinder here lies in the body/rangefinder mechanism not being affected by the lens brightness, right?
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Ana´s Nin